It’s not so surprising that the thing Zangetsu wanted to protect was Ichigo himself. The chapter showed some flashback of Ichigo’s training and there was a nice touching moment in his inner world as he got stabbed through but felt no pain because he “accepted” it. It WAS surprising that the Final Getsuga Tenshou is actually a merger between Ichigo and Getsuga; i.e. he becomes the attack itself. I have to change my previous view: this final attack might just finish off Aizen. With Ichigo actually sacrificing his shinigami powers with this move, he had better kill of Aizen or he’d be stuck using hollow powers. Aizen is at his final evolution (I wonder if he’s still going to use his bankai), and Ichigo as well has taken on a completely different form. His sword has vanished completely and the black Getsuga swirls around him, also turning his hair black.
Aizen knows that things are going out of his control, and he realizes finally that Ichigo has completely surpassed him. He rages and screams in vain as Ichigo uses “Mugetsu”. I honestly think he’s pretty much finished here, and if Aizen manages to escape this, he’ll probably have to slink away somewhere and recuperate for a few months. Of course, Ichigo still has to do something about that Hougyoku or we might be in for a lot more “wish-fulfilling” crap. This is a very high climax of the series and with the loss of Ichigo’s shinigami powers it seems like a good place for some closure. I wish that Aizen would just die, and there would be a resolution (perhaps a flashback of his past), then the end of the series instead of a new arc.